Infrared thermometers are widely used in industry and daily life to measure the temperature of an energy zone on a surface of an object. However, when the infrared thermometer is used to measure the temperature of the energy zone, since the infrared ray cannot be seen, the energy zone can only be sighted by taking the infrared thermometer as close to the energy zone as possible, or by observing the position of the energy zone relative to the infrared thermometer. This sighting method cannot align an infrared detector of the infrared thermometer with the energy zone accurately, thereby affecting the accuracy of the measurement result.
Some infrared thermometers deploy a laser sighting device to align the infrared detector of the infrared thermometer with the energy zone. Such infrared thermometers can emit a laser beam to the energy zone to be measured to form a light spot (i.e., a red dot) for alignment on the surface of the energy zone. Accordingly, it can be determined whether the infrared detector is aligned with the energy zone by observing the position of the light spot relative to the energy zone and overlapping of the two. However, the energy zone may emit visible light of a high luminous intensity, such as when the temperature of the energy zone is high, for example, one thousand degrees Celsius or more. The visible light emitted from the energy zone may affect the observation of the light spot on the energy zone, which adversely affects the alignment of the infrared detector with the energy zone.